1. Field of the Invention
This invention relates to a rotary tool adapter to be attached to a machine tool.
2. Description of the Prior Art
In a conventional bent rotary tool adapter used for a turret lathe, first and second rotary shafts 42, 43 are inserted in the shape of the letter "T" through a hollow of a T-shaped cylindrical casing 41 and supported on ball-and-roller bearings 44, 45 respectively as shown in FIG. 6, in such a manner that these shafts 42, 43 can be rotated. A bevel gear 46 mounted fixedly on the free end portion of the first rotary shaft 42 and bevel gear 47 mounted fixedly on the second rotary shaft 43 are meshed with each other.
The base end portion of the first rotary shaft 42 projects outward from the casing 41 so as to be connected to a driving shaft in a head of a machine tool, and the free end portion of the second rotary shaft 43 also projects outward therefrom and is provided with a socket 48 with which a rotary tool is to be engaged.
This rotary tool adapter is set on a rotary tool mounting portion of a head of a machine tool. During this time, the first rotary shaft 42 is joined to a driving shaft in the head, and a suitable rotary tool is engaged with the socket 48 formed at the free end portion of the second rotary shaft 43. When the driving shaft in the head is rotated, the first rotary shaft 42 is rotated, and then the second rotary shaft 43 via the bevel gears 46, 47, so that the rotary tool processes a workpiece as it is rotated.
In a conventional straight speed-increasing rotary tool adapter, an input shaft 52 and an output shaft 53 are inserted from the opposite ends of a cylindrical casing 51 thereinto and supported rotatably on ball-and-roller bearings 54, 55 respectively as shown in FIG. 7. The inner end portion of the input shaft 52 is formed cylindrically, and a suitable number of planetary roller insert holes are formed in the cylindrical wall of the inner end portion, in such a manner that these holes are spaced at regular intervals in the circumferential direction thereof. A fixed race 56 is attached to the portion of the inner circumferential surface of the casing which is opposed to the planetary roller insert holes, and the inner end portion of the output shaft 53 is inserted into the interior of the cylindrical portion of the input shaft 52 to form a sun roller 57. The planetary rollers 58 inserted rotatably in the holes in the input shaft 52 contact the fixed race 56 internally, and the sun roller 57 externally.
The outer end portion, which projects outward from the casing 51, of the input shaft 52 is formed so as to be joined to the driving shaft in the head of a machine tool, while the front end portion, which projects outward from the casing 51, of the output shaft 53 is provided with a socket 59 with which a rotary tool is to be engaged.
This rotary tool adapter is set on a rotary tool mounting portion of a head of a machine tool. During this time, the input shaft 52 is joined to a driving shaft in the head, and a suitable rotary tool is engaged with the socket 59 formed in the output shaft 53. When the driving shaft in the head is rotated, the output shaft 53 is rotated at an increased speed via the input shaft 51 and a planetary roller mechanism (fixed race 56, planetary rollers 58 and sun roller 57), so that the rotary tool processes a workpiece as it is rotated at a high speed.
This conventional bent rotary tool adapter is incapable of cutting a workpiece at a high speed when the workpiece consists of aluminum or brass, and it requires a rotary tool having a speed increasing mechanism. A straight speed-increasing rotary tool adapter is incapable of processing a surface parallel to the driving shaft in the head of a machine tool.
According to the conventional techniques, it is necessary to prepare a lot of rotary tool adapters of various specifications in accordance with the directions in which surfaces to be processed extend, dimensions of the spaces in tool heads, dimensions of rotary tools and rotational speeds of rotary, tools. Providing comparatively expensive speed increasing mechanisms for each model of rotary tool causes an extraordinary high cost increase.